The objective of this research program is to solve selected key technical problems in radiation therapy that limit the effectiveness of present treatment. The proposed research program consists of the following interdependent research projects. Projects proposed in Treatment Planning are: Measurements of Anatomical Inhomogeneities, Improvements in Dose Calculation Methods, Human-Engineered Minicomputer System for Improved Display and Three-Dimensional Treatment Planning, and Treatment Synthesis. Projects proposed in Treatment Delivery are: Dose Optimization by Computer Controlled Radiation Treatment; Electromechanical Components, System Dynamics, and Control Strategies for Automated Radiotherapy System; Radiation Therapy Field Scanning/Imaging System; and Patient Localization by Computer Tracking of Skin Markers. A project in Systems Safety and Reliabiltiy is also proposed. The problems selected satisfy the criterion that the successful outcome of each project will contribute to an advance in the quality of routine radiation therapy and, as part of the overall program, will also lead to new and improved capabilities in treatment planning and dose delivery for optimizing dose to the tumor while minimizing exposure to healthy tissues.